Electronic devices such as smart phones, laptops, remote controls, tablets, smart cards, etc., uses fingerprint recognition e.g. to allow a user to access the device, to authorize transactions carried out using the electronic device, or to authorize the user for accessing a service via the electronic device. Hence, the electronic device is equipped with a fingerprint sensor on which the user places her finger in order for the sensor to capture an image of the fingerprint and compare the recorded fingerprint with a pre-stored, authenticated fingerprint template. If the recorded fingerprint matches the pre-stored template, the user is authenticated and the smart phone will perform an appropriate action, such as transitioning from locked mode to unlocked mode, in which the user is allowed access to the smart phone.
Now, for fingerprint sensors which do not require to be physically pressed in order to be activated—i.e. the sensor is activated when the sensor detects that an object is touching the sensor—various objects may unintendedly activate the fingerprint sensor.
This has the unfortunate effect that if the user is carrying the phone in e.g. a pocket or in a bag along with other items, the sensor may be activated by objects other than a finger touching the fingerprint sensor, e.g. cloth from the pocket/bag or other items therein such as coins, keys, wallets, etc.
This unintended activation of the fingerprint sensor may for example have as a consequence that the phone vibrates in the pocket/bag, that the battery is drained from power more quickly due to the attempts to match the captured pocket/bag item images to fingerprint templates, and/or that the phone sets the fingerprint sensor in a locked mode (due to too many failed activations), requiring the user to enter a backup pin code when the phone is retrieved from the pocket/bag and the user wants to activate it.
There is thus a need in the art to determine whether an object contacting the fingerprint sensor is a finger or not.